Aside from towy has mentioned.
My experience principally being of Currys and PCWorld, in part as Dixons seems to have disappeared from the high street.
Currys: unless I can find it for myself and guide the staff to it, I'm out of luck.
PCWorld: very much pot-luck, in the past I have found an item I wanted but haven't been able to buy it because it was not priced and none of the staff available could find a price for it. OTOH I have twice stumbled across helpful and knowledgeable staff in PCWorld, though I haven't bothered to mention Linux, as I didn't want to push my luck.
Then again, local computer stores frequently aren't any better if the proprietor (and font of all knowledge) doesn't happen to be in. Otherwise ink cartridges seem to be about the limit of their competence.

Linux Emporium has been good for me in the past though. But of course, most of that has been ordered on-line.

Edit: perhaps you could pop into PCWorld and ask them if the Android tablet will work with Linux.

Certainly in PC World, I've ordered one for collection today. Beware of their new account system's lack of security. After placing the order it sent me an email with login details for the account and advice to change he password. All well and good but after I changed the password, it sent me a confirmation email, also a good idea, except it included my new password in plain text!

"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)